The present disclosure relates generally to cooking appliances and more particularly to broilers for cooking appliances.
Generally, heating elements in, for example, an oven cavity of a cooking appliance should efficiently and evenly direct heat towards food items being cooked. However, conventional heating elements such as, for example, sheath heaters, halogen lamps, and quartz lamps, transmit heat in all directions with much of the heat being absorbed by the oven cavity walls. This generally results in heat not being delivered efficiently and directly to the food, as well as extreme heat gradients where food is unevenly cooked across its exposed surface. Radiant ribbon heaters transmit heat more directional and can be more efficient in delivering heat directly to food, but they are generally sluggish since they require a backside insulative mat to support and position the ribbons and have a fair amount of heater mass to overcome. It is also the nature of the ribbons to be aligned width-wise in parallel with intended radiation path to the food rather than the more efficient perpendicular orientation.
Recently, there have been several advances in a variety of infrared quartz tubular heaters called carbon emitters that are produced by companies such as Panasonic and Heraeus Noblelight. These heaters, while encased and sealed in an inert gaseous environment, use a wide, yet flat carbon filament that heats up quickly and intensely when current is applied. The carbon filaments, which are generally made of carbon fibers and carbon dominated matrices, are very low in mass, and can heat up in less than 3 seconds and exhibit no adverse in-rush characteristics that tend to plague some of the more traditional heaters that principally use metallic filaments such as tungsten. For example, a standard quartz heater that uses a tungsten filament may have an in-rush current spike of 10 A compared to its eventually steady state current of 1 A.
Carbon emitters, while having no substantial in-rush surges, are also very directional in their ability to apply heat since the filaments are very thin and very wide. They are extremely efficient when the filaments within the tubes are placed in a perpendicular direction relative to the radiation path to the object being heated. There are industrial applications of carbon emitters. For example, carbon emitters have been used to dry coatings. However, they have not been used in either the commercial or residential appliance industry. With the need to limit demand peaks at the utilities and the difficulties to build new power plants in the US, the carbon emitter technology provides an opportunity to reduce the wattage required to adequate cook or broil food by more efficiently directing heat from the broiler above the food down onto the food.
It would be advantageous to be able direct heat efficiently and more evenly to the food being cooked within an oven cavity.